Audio reproduction methods and apparatus

ABSTRACT

Methods and apparatus for reproducing audio information wherein the information is provided on a medium, such as paper, in the form of encoded audio lines wherein these lines are scanned to reproduce the audio information therein. Also provided is method and apparatus of producing the audio information from a particular preselected audio line of a field array of audio lines in response to the preselection of this line.

United States Patent 1 1 Shutterly Oct. 30, 1973 [54] AUDIO REPRODUCTION METHODS AND 3,335,219 8/1967 Goldmark et al 178/6.7 A APPARATUS 2,538,869 1/1951 Holst 179 1003 r 2,575,445 11/1951 Genner 179/1003 A [75] Inventor: Harold B. Shutterly, Pittsburgh, Pa.

[73] Assignee: Westinghouse Electric Corporation, primary Examine, Raymond p Cal-dine, 1L

' pmsburgh Attorney-F. H. Henson et a1. [22] Filed: July 30, 1971 [21] Appl. N0; 167,742 57 ABSTRACT Methods and apparatus for reproducing audio infor- [52] 179/1003 178/6] mation wherein the information is provided on a me- [51] Int cl Gllb 7/02 H04 5/84 dium, such as paper, in the form of encoded audio [58] 179/100 3 B lines wherein these linesare scanned to reproduce the audio information therein. Also provided is method 5 5 6 and apparatus of producing the audio information from a particular preselected audio line of a field [56] References Cited array of audio lines in response to the preselection of UNITED STATES PATENTS 8 me 3,300,591 1/1967 Gushue et al. 179/1003 B 2 Claims, 9 Drawing Figures RESET AT END PRE-SET OF EACH FROM SCAN LINE PUSH BUTTONS I HASE NS'iAiE (26 ADVANCE OSCILLATOR ADJUST STAGE COUNTER E CIRCUIT COUNTER (REFERENCE) EACH 11 J J i6 203 1 i l4 ADBER ADEER ADDER N PP QBQ E OADDERS LIMITER I T I) 2a CHECKS FOR '2 A ALL INPUTS=Q 3o COMPOSITE AUDIO SAMPL'NG -waumo OUTPUT L SAMPLES PER SCAN GATE SAMPLES AT WHERE L IS THE N0.0F SCAN LINE AUDIO LINES SCANNED RATE PAIENIEIIIIBISO I973 3.769.468

SHEET 10? 2 M I I 'l SCANNING AMPLIFIER O E DEVICE PROCESSOR AUDI L AUDIO OUTPUT I AUDIO REPRODUCTION VARIABLE-DENSITY AM SCANNING SPOT SCANNING PATH III! I I IIHIIIHI I I IIIIIIII I. I II II D'G'TAL CODE SCANNING PATH III I IIIIIIAI IIII II I III IIIIIy'I IlII II I I SCANNING SPO SCANNING DIRECTION FREQUENCY MODULATION IIIIII/IAIIIIIIIIIIA 4 UUI/U UUIJUIIUV/ SCAN LINE PRINTED AUDIO LINE VARIABLE DENSITY AUDIO SIGNALS I FIGY. 5

PATENTEHIJCI 30 I975 3.789.488

.SHEEI 2 [1F 2 PRINTED LINE WIDTH k RASTER WIDTH+-' AI- A2 A 2 FIGS SCAN LINE RETRAcE REsET AT END PRE-SET OF EACH FROM scA LINE PUSH BUTTONS- 32 34 I I I III I26 ADVANCE PHASE N STAGE N-STAGE |COUNT oscILLAToR ADJUST COUNTER AT END OF cIRcuIT COUNTER (REFETENCE) EACH FIELD I6 20 II22 I24 ADDER ADDER AJDER PEEBQ E I4 LIMITER I FIG 7 CHECKS FOR ALL |NPUTS=0 l0 '2 3Q v COMPOSITE AUDIO A'gQE J-PAUDIO OUTPUT L SAMPLES PER SCAN I F SAMPLES AT WHERE L Is THE NO. OF SCAN-LINE AUDIO LINEs SCANNED RATE SYNC , BURST I LINEs FIG.8

AUDIO- LONG RAsTER LINEs AUDIO REPRODUCTION METHODS AND APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention'relates to methods and apparatus of audio reproduction and, more particularly, to such methods and apparatus for the optical scanning and reproduction of audio information in predetermined formats.

2. Description of the Prior Art A useful teaching technique could be implemented by providing descriptive material in pictorial or verbal form on one side of a planar medium, such as paper or plastic, and also providing on this medium preferably on the opposite side to the descriptive material audio information in suitable form to be reproduced for the user in correspondence to the printed material. One means for providing the audio information would be to dispose on the other side of the medium a line pattern whose width corresponds to the audio intelligence encoded therein. In other words, the line would correspond to an amplitude modulated signal whose intensity varies with the intensity of the audio intelligence and whose undulations correspond to the variations of the audio information. Such an amplitude modulated audio line could be sensed optically by a scanning device such as a television camera or a flying spot scanner, with the scanning occurring along the longitudinal length of the line. The electrical output of the optical scanning device would thus correspond to the width of the line, that is, according to the amplitude of the audio information and would thus be capable of reproducing the audio information encoded therein. In such an arrangement, however, it is necessary that the scanning beam be accurately positioned with respect to the center line of the amplitude modulated line. Otherwise, the output of the scanning device will not correspond to the amplitude, that is, the width of the audio line. This problem can be somewhat minimized by increasing the size of the scanning beam so that a slight misregistration of the beam and the line will not introduce serious errors in the output of the scanning device. The use of the larger beam, however, would cause the readout resolution of the scanning device to be reduced and correspondingly result in a lower audio recording density being provided. Another solution might be through the generation of an elliptical scanning beam having its major axis perpendicular to the length of the audio line. However, it is relatively difficult to generate such an elliptical beam and to maintain its orientation relative to the line throughout the entire scan of the line. Moreover, the employment of a large beam size of either circular or elliptical shape would permit much of the nonprinted portion of the medium to be sensed which would tend to decrease the audio signal-to-noise ratio at the output of the scanning device.

If the medium described above having descriptive material on one side and audio information on the other side were employed in a teaching environment wherein the student could selectively respond to the descriptive material, it would be highly desirable if an audio output could be provided corresponding to the nature of the student input. For example, if the student response was a correct one an audio output indicating this correctness would be provided. Alternately, if an incorrect response were entered by the student, this would be indicated by reading out the selected audio information on the backside of the medium and perhaps supplying the student with the remedial audio material. It would thus be highly desirous if random access could be afforded to recorded audio information on the medium which could be selected in response to the students response. It would also be highly important that slight misplacements of the medium within the teaching apparatus would not seriously affect audio output of the apparatus.

SUMMARY OF THE INVENTION Broadly, the present invention relates to method and apparatus for the reproduction of audio information wherein information is provided on a medium in such a manner to afford accurate reproduction thereof by minimizing the alignment accuracy required between the medium and the scanning device and also to provide the random access to the audio information.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a simplified block diagram illustrating ageneral embodiment of the present invention;

FIGS. 2, 3, and 4 are waveform diagrams indicating various techniques by which audio information may be provided upon the mediiim of the present invention;

FIG. 5a is a pictorial diagram of an amplitude modulated audio line;

FIG. 5b is a pictorial diagram of a narrow width variable density audio line;

FIG. 6 is a pictorial diagram illustrating a scanning sequence as employed in the present invention;

FIG. 7 is a block diagram illustrating the random access feature of the present invention; and

FIG. 8 is a pictorial diagram illustrating another feature of the present invention with reference to FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram of the general arrangement of the present invention wherein a medium M, which may comprise a planar sheet of paper or plastic or other equivalent material, has disposed on one side thereof a plurality of audio lines A1, A2, A3, An. On the other surface of the medium M could be disposed descriptive material for presentation, for example, to a student, such as pictorial information, aprinted page of instructional and/or testing material.

The lines A1 An may be disposed on the medium M according to a line distribution format as shown in FIGS. 2, 3, and 4. In the embodiment of FIG. 7, the lines A1 An may take the form of amplitude modulated lines such as shown in FIG. 5a or variable density lines as shown in FIG. 5b.

The audio lines A1 An respectively include audio information which may correspond to the descriptive material appearing on the other side of the medium M. The audio information in the lines Al An is sensed via a scanning device S which may comprise a television camera or a flying spot scanner including a photoresponsive element to sense the reflection from the audio lines A1 An. The scanning device S is so operated to scan the audio lines Al An from left to right or right to left along each of the lines when the line distribution format of FIGS. 2, 3, and 4 is employed. When the amplitude modulated (5a) or narrow-width variable density type of line format (5b) is employed,

the scanning device S may be operative to scan successively line-s Al, A2, A3, An according to the field scan pattern as shown in FIG. 6, with this type of scanning being implemented by the system as shown in FIG.

The output of the scanning device S is indicative of the audio intelligence included within the audio lines A1 An. The output of scanning device S is applied to an amplifier processor AP for suitable amplifying and processing and then is applied to an audio reproduction device AR which may comprise an electrodynamic speaker. Thus, by suitably optically scanning the audio lines A1 An via the scanning device S, the audio intelligence included therein may be audibly reproduced.

If the audio lines are to be scanned along their longitudinal length (i.e. from left to right or right to left), it is necessary that the scanning device S be properly aligned therewith. In order to make it relatively easy to align the scanning device S with the audio lines, even should the medium M be disposed at slightly different relative positions thereto at one time or another, a fixed-width wide line distribution type of recording on the medium M for each of the audio lines Al-An, is employed as shown in FIGS. 2, 3, and 4. The fixed-width line distribution type of recording provides a relatively wide line of substantially constant width wherein the audio intelligence is encoded therein by variations in intensity of the line distribution along the longitudinal axis of the line. For example, a high density of lines in the line distribution may be indicative of a high amplitude audio and a low density line distribution may be indicative of low amplitude audio. The variations in density along the line will be indicative of the amplitude changes of the audio.

A variable density modulated type of line distribution is shown in FIG. 2. The scanning beam of the scanning device 8 would scan along the indicated scanning path. The density of the recorded line varies directly with the audio information content thereof. The width of the line distribution, however, is substantially constant. One technique for recording intially such an audio line would be to drive a strip of paper moving at constant speed past an ink pen driven back and forth at right angles to the paper motion and frequency'modulated in accordance with the audio information being recorded.

The scanning device S of FIG. 1 scanning such a line distribution of variable density as shown in FIG. 2 would provide an amplitude modulated audio output to the amplifier processor AP for amplification therein and then would be supplied to the audio reproduction AR with the audio output being directly provided thereby in response to the variable density line distribution as shown in FIG. 2.

FIG. 3 shows a digitally coded type of line distribution having a substantially constant width but the density of lines being determined in response to a digital code. For example, a technique of recording such a line distribution as shown in FIG. 3 would be to gate ON and OFF a high frequency carrier signal which energizes the activation of the pen in an ink recorder. The carrier frequency would be selected high enough so that one or more cycles of the carrier would be completed in the time of each pulse of the digital code. In FIG. 3, the digital code line distribution is shown spread out for-purposes of example, however, in actual practice the recorded line distribution would be closely spaced. The reproduction of recorded information as shown in FIG. 3 would be the same as that of FIG. 2 with the scanning device scanning the selected line from along its length.

FIG. 4 shows a frequency modulated line format for recording the audio lines A1 An on the medium M of FIG. 1. In the format of FIG. 4, the frequency of a carrier is modulated in accordance with the amplitude of the audio information to be recorded. The higher the amplitude of the audio, the higher the frequency of the recorded line distribution and vice versa. As in the case of FIG. 3, the line distribution of FIG. 4 is shown widely spaced for purposes of illustration. In practice the lines would be closely spaced according to the frequency modulation in order for the scanning device S to provide an output corresponding to the audio information included in the information recorded in the audio lines.

The employment of the wide-line format as shown in FIGS. 2, 3, and 4, has the advantage that the scanning path along the length of the line does not have to be exactly aligned with the center line of the line in order to provide a' proper representation of the audio information recorded in the line. Moreover, the scan line need not scan the line distribution perpendicularly to the individual lines of the line distribution but may traverse the line distribution at an angle with respect to the individual lines of the line distribution format and still provide an audio output corresponding to the originally reported audio information. Thus, exact alignment of the medium M with respect to the scanning device S is not as critical as would otherwise be the case if a narrow width line format were employed such as shown in FIGS. 5a and b and the scan direction is along the length of each of the individual lines A] An, as shown in FIG. 1. Also, the scanning spot size can be very small so that the information density in the horizontal direction can be high.

The use of the wide-line format as shown in FIGS. 2, 3 and 4 results in a relatively poor line density when a plurality of such wide lines are disposed in paralle. This problem is minimized by employing the scanning and sampling techniques of thepresent invention wherein the scanning device S is made to scan from line to line, such as shown in FIG. 6, rather than along the length of the given line, such as indicated in FIGS. 2, 3, and 4. The respective lines Al An may be encoded according to variable density technique such as shown in FIG. 5b or may be encoded with width modulation such as shown in FIG. 5a. By the employment of the narrow width lines as shown in FIGS. 5a and 5b the reduced space required for each line permits better utilization of the total recording area on the medium M and resultsin a higher audio density for a given surface area employed. In the following discussion with respect to FIGS. 6, 7, and 8, it may be assumed that the audio lines A1 An are deposited upon the medium M either by the variable density techniques discussed with respect to FIG. 5b or the amplitude width modulation as shown in FIG. 5a.

FIG. 6 shows a field of audio lines A1 An disposed parallel to one another. The audio information included in each of the audio lines is read out by employing a scanning raster via the scanning device S in FIG. 1 in a manner similar to a television raster wherein the scan lines across the audio lines A1 An substantially perpendicular thereto and then retrace in a nonscanning fashion to again scan the audio lines perpendicular thereto in a second line of scan, etc. Each scan line accordingly provides one sample from each of the audio lines as it crosses it, so that a composite audio output is provided comprising samples from each of the lines A1, A2,"A3 An, respectively, for a given line of scan, and then the same sequence of samples for the next line of scan, etc.

As is well known by sampling theory, if an audio signal is sampled at a rate of at least twice the highest audio frequency, then the audio intelligence may be recovered. If it is assumed that the highest recorded audio inforamtion on the various audio lines is 3 KHz and was recorded on the medium M, then the audio information may be recovered by sampling at a 6 KI-lz rate or higher. If'an original recording on the medium M was selected to be 30 inches per second at a 6Kl-Iz sampling rate, this would permit 5 X inches per sample which would afford a scan line spacing of 5 mils. A line scanning rate of higher than 6 KHz could also be employed providing that the spacing between the scanning lines was accordingly reduced, that is, the product of the sampling frequency and the scan line spacing must be equal to the rate at which the audio lines were originally deposited upon the medium M, which in our example, is given as 30 inches per second.

In order to reconstruct the audio information from a selected line out of the field of audio lines, it is necessary that the audio samples from the selected line be recovered from the composite audio output including samples from all the lines. This may be accomplished in the following manner with reference to the block diagram of FIG. 7.

The composite audio output which would be provided by the amplifier processor AP of FIG. 1 resulting from a scanning raster as shown in FIG. 6 would be applied to a sampling gate 10 of FIG. 7. The sampling gate 10 is so controlled in response to a gating input 12 thereto to select from the composite audio input thereto, the audio samples from a given one of the audio lines which is preselected as will be described.

The composite audio output applied to the sampling gate 10 comprises a chain of pulses varying in amplitude or width according to the audio intelligence sampled from their respective lines. The composite audio is also applied to a limiter 14 which amplitude limits each of the sample pulses in the composite signal to provide equal amplitude pulses at the sampling rate of the audio lines A1 An. The limited output is applied via a switch 16 to the input of an n-stage counter 18. The n-stage counter 18 must be of a sufficiently high number of stages in order to provide a sufficiently high binary number count in excess or equal to the number of audio lines A1 An. For example, a three stage binary counter as illustrated in FIG. 7 would provide a number count of seven before resetting. If an eight stage binary counter were employed, 255 audio lines could be scanned according to the teachings of the present system.

As shown in FIG. 7, each stage of the counter provides an output to adders 20, 22, and 24, respectively. The other input to the adders 20, 22 and 24 is from the respective stages of a reference n-stage counter 26. The n-stage reference counter 26 may have the same number of binary stages as the counter 18. The reference 1 counter 26 is capable of being preset via pushbuttons,

for example, by the user to select any of the audio lines Al An. Thus, for example, is the line A6 were to be selected the input'6 would be preset into the reference counter 26. The adders 20, 22 and 24 function logically so that whenever both inputs thereto are identical, that is, both are ONEs or both are ZEROs, a ZERO output is provided thereby to an AND logic element 28. When the inputs to a given one of the adders 20, 22, and 24 differ, that is, one input is a ONE and the other is a ZERO, a ONE output will be received from the respective adders 20,22, and 24, to the AND gate 28.

The AND gate 28 is responsive to all ZEROs being inputted thereto provide a ONE output 12 to the sampling gate 10. In sum, if there is coincidence of inputs to each of the adders 20, 22, and 24, each will provide a ZERO output to the AND gate 28, which in response thereto, will provide a ONE output 12 to the sampling gate 10.

The counter 18 counts each of the samples provided thereto. With the number 6 being preset into the reference counter 26, one or more of the adders 20, 22, and 24 will provide a ONE output to the AND gate 28 disabling it from provide a ONE output at 12 until the sixth pulse is counted by counter 18. When the n-stage counter 18 reaches the sixth count, there will be coincidence between the outputs of each of the stages of the counter 18 and the reference counter 26 so that the adders 20, 22, and 24 will each provide a ZERO output to the AND gate 28 which will provide a ONE output 12 to gate ON the sampling gate 12. The sampling gate 10 will thus provide the sampled pulse from the sixth line A6 at the output 30 thereof which is indicative of the audio intelligence in the sixth audio line. All other lines of the array of audio lines would be blocked by the sampling gate 10.

A signal is provided to the counter 18 to reset it at the end of each scan line, that is, after the line An has been scanned in the raster as shown in FIG. 6. Thus, at the beginning of each line of scan, commencing at the line Al the counter 18 will be reset to zero to again commence the counting operation. When the counter 18 again reaches the sixth count, coincidence will exist again which will cause the sampling gate 10 to be opened to translate the then existing sampled audio from thesixth' line to appear at the output 30. This operation will continue until a complete field of scan has been completed. An advance input may be provided to the reference counter 26 at the end of each field of scan to advance automatically the preset count in the reference counter 26 by one count, that is, in the present example, it would advance from the count 6 to the count 7 so that the seventh line would be sampled from the audio lines if another preset input were not provided to the reference counter 26 after the sampling of the line A6 had been completed.

The scanning raster as shown in FIG. 6 may be translated somewhat with respect to the printed audio lines without adverse affects in that these lines correspond to a continuous analog signal. As is well known from sampling theory in sampling periodically a continuous waveform, the phase of the sampling is unimportant as long as the samples are taken at a sufficiently high rate. Some noise, however, may be introduced into the recovered audio information if the scanning raster is so out of position that a number of scan lines miss the printed audio lines completely. This problem is solved in FIG. 6 by making the scanning raster width slightly shorter than the width of the printed lines. Hence, a slight shift of the printed lines with respect to the scan raster will merely bring the scan raster closer to the end I of the printed audio lines.

It is possible that a certain amount of noise may be introduced-duringthe field retrace time since no samples are taken during this period. However, this can be minimized by making the field retrace time very short. If the field retrace time is made equal to one line retrace time, then no gaps will occur in the sampling from the last sample of line An to the first sample of line A1.

Alternatively the direction of the field scan could be reversed at the end of each field and thereby eliminate field retrace time. This field reversal scan sampling would require a similar type of recording scan.

The format of FIG. 6 also provides a reasonable degree of tolerance to positional errors causing the lines Al An to shift upwardly or downwardly by making the scan lines longer than the distance between lines Al and An.

A slight tilt of the raster relative to the printed audio lines can also be tolerated because the n-stage counter 18 is activated in response to each of the audio lines being crossed and the sampling gate 10 is open in response to correlation of the counter 18 and the reference counter 26. Thus, as long as the tilt is not excessive, proper functioning of the system will still occur.

Referring again to FIG. 7, if it is desired to very accurately take the samples of the various audio lines at the center line thereof, the switch 16 may be switched to its other position so that the output of the limiter 14 is applied to a phase lock oscillator 32 whose frequency is set so that the period of the output signal therefrom is equal to the time required to scan from the center of on'e of the printed audio lines to the center of the next of the audio lines. A phase adjust circuit 34 is connected between the output of the oscillator 32 and the input of the counter 18 to compensate for slight shifts in phase. The phase of the oscillator can be maintained by providing a few unmodulated reference lines B1, B2, B3, B4 at the beginning of each line of scan as shown in FIG. 8. This is analogous to the function of the color burst signals in color television receivers. The reference burst produced in response to scanning the lines B1, B2, B3, and B4 is passed through the limiter 14 so that the audio samples following thereafter would continue to hold phase.

Also shown in FIG. 8 is a lead-in sync line SY which may be a relatively wide line as compared to the other lines and may be employed for enabling the n-stage counter 18 after being reset at the end of a complete line of scan. The format thus as shown in FIG. 8 would comprise the wide sync line SY followed by the four reference lines B1, B2, B3, and B4 for phase control and then the scanning of the audio lines Al An in the manner as described above.

l claim:

1. Apparatus for reproducing audio information comprising:

a medium including a plurality of audio line distributions each respectively indicative of audio information, said plurality of line distributions being arranged in a field to be substantially parallel to one another;

means for developing a scanning raster for sweeping across said medium and including scan lines for traversing said plurality of line distributions of said field and deriving samples of audio information at the intersections of said scan lines and said plurality of line distributions to provide a composite output indicative of the audio information sampled from each of said plurality of line distributions intersected, said composite output including a sample from each of said plurality of line distributions scanned; and

means for selecting from said composite output the audio information indicative of a preselected line distribution from said plurality of line distributions for audio reproduction, said means for selecting including, sampling means for receiving said conposite output, input means for counting said samples in said composite output and providing an input count output in response thereto, reference means operative to be preset to a reference count output in response to an input thereto to select said predetermined of said plurality of line distributions, and means responsive to the relationship of said input count output and said reference count output to provide a sampling output to said sampling means to permit said sampling means to translate therethrough the samples corresponding to said predetermined line distribution.

2. Apparatus as claimed in claim 1, wherein said scan lines are substantially perpendicular to said line distributions. 

1. Apparatus for reproducing audio information comprising: a medium including a plurality of audio line distributions each respectively indicative of audio information, said plurality of line distributions being arranged in a field to be substantially parallel to one another; means for developing a scanning raster for sweeping across said medium and including scan lines for traversing said plurality of line distributions of said field and deriving samples of audio information at the intersections of said scan lines and said plurality of line distributions to provide a composite output indicative of the audio information sampled from each of said plurality of line distributions intersected, said composite output including a sample from each of said plurality of line distributions scanned; and means for selecting from said composite output the audio information indicative of a preselected line distribution from said plurality of line distributions for audio reproduction, said means for selecting including, sampling means for receiving said conposite output, input means for counting said samples in said composite output and providing an input count output in response thereto, reference means operative to be preset to a reference count output in response to an input thereto to select said predetermined of said plurality of line distributions, and means responsive to the relationship of said input count output and said reference count output to provide a sampling output to said sampling means to permit said sampling means to translate therethrough the samples corresponding to said predetermined line distribution.
 2. Apparatus as claimed in claim 1, wherein said scan lines are substantially perpendicular to said line distributions. 